In a fuel cell, a cell (single cell) serving as a minimum unit is formed by stacking a plurality of cell constitutional members, and by forming a stack structure in which a plurality of cells are stacked, a required voltage is secured. A separator constituted by a plate-shaped component is used in the stack structure as a member that is positioned on an outermost layer of each cell to separate each of the cells in the stack. Further, the separator functions to supply a fuel gas to an anode side and an oxidant to a cathode side, carry electricity generated by the cell, discharge generated water generated in the cell, and so on.
FIG. 18 shows an example of the cell structure of a polymer electrolyte fuel cell. A cell 10 is structured by disposing a membrane electrode assembly 12 (“MEA” hereafter) in a central portion of the cell 10 in a thickness direction, and disposing a gas diffusion layer 14 (anode side/cathode side gas diffusion layers 14A, 14C), a gas flow passage 16 (anode side/cathode side gas flow passages 16A, 16C), and a separator 18 (anode side/cathode side separators 18A, 18C) on either side of the MEA 12. Note that a structure formed by integrating the MEA 12 and the gas diffusion layer 14 may be known as a MEGA (Membrane Electrode & Gas Diffusion Layer Assembly).
In the structure of the cell 10 shown in FIG. 18, in which the gas flow passage 16 is formed as a separate structure to the separator 18, the aforementioned functions of the separator are secured by employing an expanded metal, for example, as a structure for forming the gas flow passage 16 (see Patent Documents 1 and 2, for example).
Patent Document 1: Japanese Patent Application Publication No. JP-A-2005-310633
Patent Document 2: Japanese Patent Application Publication No. JP-A-2002-198069